Why do men keep their bottom vest buttons unbuttoned?

Why do men keep the bottom button of their vests unbuttoned? I asked a male companion and he said, "just in case." Just in case what?

— Sylvia D., Oak Park, Illinois

Cecil replies:

Who knows? Maybe he figures he'll save time if he needs an emergency appendectomy. Guys don't think too clearly when it comes to the crotch region.

Several explanations have been offered for the custom of leaving bottom vest buttons undone, all partaking of a certain degree of ridiculousness. Preeminent among these is the story that a member of the British royal family once appeared at some public function with his bottom button carelessly left unbuttoned. Thinking that some bold new direction in fashion was thereby being decreed, all of the gentlemen present promptly unbuttoned their own buttons. Thus was custom born. I confess to some skepticism here.

Theory number two traces back to the days when dandys wore two waistcoats, each of some luxuriant material. In order to show off the undercoat (as it were), each dude would reveal it by unbuttoning his bottom button.

Finally, there is the explanation that old-time waistcoats were so tight that it was impossible to sit down unless you unbuttoned the bottom button. This one has a certain nuts-and-bolts plausibility to it. However, you can take your pick.